Lubricating oil compositions



Patented May 3, 1949 UNITED STATES PATENT OFFICE LUBRICATING OILCOMPOSITIONS Albert G. Rocchini, Springdale, PaL, assignor to GulfResearch & Development Company, Pittsburgh, Pa., a corporation ofDelaware No Drawing. Application July 14, 1947, Serial No. 760,943

3 Claims. (Cl. 252--32) in this type of engine. Among the several shortcomings of uncompounded mineral oils when used as lubricants in suchengines, One of the most serious is manifested by sludge formation inthe crankcase, sticking of the piston rings, and the formation ofvarnish-like coatings on the pistons and cylinder walls. Thesedifficulties are all considered to be due to oxidation of the oil underoperating conditions whereby there is formed a variety of oxidationproducts which range in physical form from a soft sludge, such asaccumulates in the crankcase, to a hard adhesive deposit whichaccumulates in back of the piston rings causing them to stick withconsequent inadequate lubrication of the cylinder walls, scoring of thecylinder walls, overheating, loss of power, etc. These difliculties maybe alleviated by adding to the oil minor amounts of certain agents whichapparently act to disintegrate and colloidally disperse the sludgethroughout the oil and thus prevent it from accumulating at any onepoint in the lubrication system- Since this action is somewhat akin tothe action of detergents in aqueous media, the agents so employed aretermed detergent additives although they are quite different chemicallyfrom the water-soluble detergents or dispersing agents commonly used inaqueous cleansing operations. In some instances these additives may alsoact to increase the oxidation stability of the oil, and thus serve theadditional purpose of decreasing the amount of oxidation products formedin the oil.

While a number of chemical products have been proposed for use asdetergent additives in compounded lubricating oil compositions, many ofsuch products have not proved sufllciently effective for use in the moremodern types of engines. Others satisfactorily effect the desireddetergent action, but at the same time disadvantageously alter thephysical properties of the oil. Still others interfere with the actionof other additives, e. g., anti -corrosion agents, pour-pointdepressants, ex-

'treme pressure agents, viscosity index improvers,

etc., or must be employed in such quantity as to increase unduly thecost of the oil.

It is accordingly an object of the present invention to providelubricating oil compositions having improved detergent properties.

Another object is to provide lubricating oil compositions containingminor amounts of detergent additives which do not adversely afiect thedesirable properties of the oil and which do not interfere with theaction of other additive agents.

A further object is to provide lubricating oil compositions which willsubstantially reduce ringsticking' and attendant difllculties ininternal combustion engines, particularly those of the Diesel type.

Other objects will be apparent from the following detailed descriptionof the invention, and various advantages not specifically referred toherein will occur to those skilled in the art upon employment of theinvention in practice.

In accordance with the above and related objects, I have found thatcertain metal salts of naphthenoxy-stearic acids have properties whichrender them admirably suited for use as detergent additives inlubricating oil compositions. More particularly, I have found that thepolyvalent metal salts of naphthenoxy-stearic acids may be incorporatedwith mineral oils of lubricating viscosity to form lubricatingcompositions which substantially reduce ring-sticking when employed inmodern internal combustion engines, including Diesel engines. Such saltsare effective in relatively small amounts so that their presence in thecomposition does not materially affect the physical properties of theoil or interfere with the action of other additive agents which may beincluded in the composition.

The term naphthenoxy as herein employed refers to the group R,COO,derived from a naphthenic acid, R-COOH, wherein R repre sents anaphthenic hydrocarbon radical, just as the term acetoxy refers to thegroup CHaCOO; derived from acetic acid, CHJCOOH. The naphthenoxy-stearicacids are thus stearic ac'ids'having an R-COO-group substituted at somepoint along the aliphatic chain. They are obtained by esterifyingnaphthenic acids with any of the isomeric hydroxy-stearic acids, ormixtures thereof, in accordance with ordinary esterification procedure.As ordinarily obtained employing a commercial grade of the naphthenicacids in the esteriflcation reaction, they are highboiling dark-coloredoily liquids, soluble in a variety of organic solvents. If desired, theymay be purified prior to use in forming the metal salts employed inaccordance with the invention, but it is usually more convenient andeconomical to employ them in crude form directly as they are obtainedfrom the esteriflcation reaction.

The polyvalent metal salts of the naphthenoxystearic acids areconveniently prepared by metathesis from the corresponding sodium orother alkali-metal salt. In preparing the intermediate alkali-metalsalt, the naphthenoxy-stearic acid is preferably first dissolved in aninert reaction medium, such as acetone, ethanol, etc., and thealkali-metal is employed in the form of an alcoholate, such as sodiummethylate, potassium ethylate, etc., or as an alcoholic solution of thehydroxide. The reaction takes place readily upon mixing the tworeactants at room temperature or slightly above. If desired, thealkalimetal naphthenoxy-stearate product may be isolated and thereafterdissolved in water and reacted with an aqueous solution of a salt of thedesired polyvalent metal to form the corresponding polyvalent metalnaphthenoxy-stearate, but

ordinarily it is more convenient simply to add water to the reactionmixture, and then add the aqueous polyvalent metal salt solution. Thedouble decomposition reaction takes place readily at ordinarytemperatures, and the polyvalent metal naphthenoxy-stearate precipitatesout of solution, and may be separated and washed free of solublecontaminants. Any water-soluble polyvalent metal salt may be employed toobtain the corresponding metal naphthenoxy-stearate in this manner, e.g., barium chloride, calcium chloride, zinc nitrate, ferric chloride,strontium nitrate, aluminum sulphate, magnesium bromide, manganesechloride, lead nitrate, copper sulphate, chromium chloride, antimonychloride, cobalt nitrate, nickel chloride, cadmium nitrate, tinchloride, etc., and any of the oil-soluble metal salts so obtained maybe used in accordance with the invention. By reason of their generalavailability and low cost, the metals of groups II and VIII of theperiodic system are usually preferred.

In compounding the improved lubricating oil compositions provided by theinvention, the desired metal naphthenoxy-stearate is added to the baseoil in an amount sufficient to secure the desired degree of improvementin the service characteristics of the oil. This amount will accordinglydepend upon the characteristics of the oil itself, as well as upon theconditions to which the composition is subjected in use. Ordinarily,however, the metal salt additive is employed in an amount representingbetween about 0.1 and about 5.0 per cent by weight of the entirecomposition. If the composition is to be employed in more or lesslight-duty operations, e. g., in automobile engines, the amount of theadditive is usually at the lower end of this range, whereas compositionsto be used in heavy-duty gasoline or Diesel engines will containsomewhat larger proportions of the additive. The base oil may be anyhydrocarbon oil of lubricating grade and viscosity obtained by any ofthe modern refining methods from paraffinic, naphthenic, asphaltic, ormixed base stocks, or it may be a synthetic lubricating oil produced,for example, by the polymerization of olefins.

As previously stated, the detergent additives of the present inventionfunction independently of other types of additives without materiallyaltering the physical characteristics of the oil. Accordingly, the baseoil may contain other additive agents, such as viscosity indeximprovement agents, pour-point depresants, bearing corrosion inhibitors,oxidation inhibitors, extreme pressure agents, anti-foam agents, etc.The nature of such additives and the proportion in which they areemployed, as well as the characteristics of the Example INaphthenoxy-stearic acid was prepared by dissolving 300 parts ofhydroxy-stearic acid, 250 parts of a naphthenic acid having aneutralization equivalent of 200, and 5 parts of p-toluene-sulfonic acidin 173 parts of toluene. This mixture was heated at reflux temperaturefor 24 hours, during which time 16 parts of water formed in the reactionwere recovered. The mixture was then treated with anhydrous sodiumcarbonate to neutralize the acid catalyst, and the solids were filteredofi. After distilling off the toluene, the naphthenoxy-stearic acid wasobtained as a darkcolored high-boiling oily liquid. This product wasdiluted with about A; of its volume of acetone, and 68 parts of sodiumethylate dissolved in ethyl alcohol were added with stirring, wherebythere was formed a brown precipitate of sodium naphthenoxy-stearate.Sufficient water was added to the mixture to dissolve this precipitate,and 150 parts of nickel nitrate dissolved in water were added withstirring, whereby there was formed a dark precipitate of nickelnaphthenoxy-stearate. The supernatant liquid was decanted and theprecipitate was dissolved in hexane and washed with water. It wasrecovered as a greenish-brown viscous liquidby evaporating off thehexane. 'It contains 5.5 per cent nickel by analysis. A lubricating oilcomposition typical of those provided by the invention was prepared bydissolving 3.3 parts of the nickel naphthenoxystearate in 96.7 parts ofa solvent-refined Mid- Continent oil. The physical properties of thiscomposition, together with those of the base oil,

were as follows:

I Base Oil+ Base Oil 3.3%

Additive Gravity, API 26. 5 27. 7 Viscosity, SUS at- 100 F 463 508 206224 210 F.. 59. 9 62. 4 Viscosity Index 88 90 Flash Point, F 470 470Fire Point, F 525 5'30 Pour Point, F +20 I +5 Color, NPA 2+ 3. 5- CarbonResidue 0.05 i 0.29 Neutralization Number i 0. 0i 1 0. 06 Ash, Per Cent0.01 0.20

This composition was tested in a standard Lauson engine for ability toprevent ring-sticking. The Lauson test consists in placing 2.1 1bs.,0fthe composition in the crankcase of a single cylinder Lauson Dieselengine. The engine is operated under a 3 H. P. load at 1850 R. P. M.,maintaining a cooling jacket temperature of 300 R, an oil temperature of225 F., and an air-to-fuel ratio of 13:1. At the end of 24 hoursoperation, the engine is stopped, disassembled, and the piston isexamined as to stuck rings and discoloration. If there are no stuckrings, the engine is reassembled, the oil charge is brought up to 2.1lbs., and operation is continued for another 24- hour period. Thisprocedure is repeated until one of the rings sticks or until a total of216 operating hours hasaccrued. The piston color is rated on anarbitrary scale of 10 to representing increasing discoloration of thepiston skirt. The data obtained in this test, together with compara- Alubricating oil composition similar to that described above in Example Ibut containing only 1.7 per cent of the nickel naphthenoxy-stearate wasfound to be equally efiective in preventing ring-sticking in the Lausonengine test. With a third composition containing 0.83 per cent of theadditive, ring-sticking occurred only after 120 hours of operation inthe Lauson engine.

While the compositions described above were formulated for testingpurposes, and thus contained only the base oil and the polyvalent metalnaphthenoxy-stearate additive, it will be understood that compositionsfor various commercial applicati ns will usually also contain otheradditive agents, particularly oil-soluble corrosion inhibitors. Thefollowing examples are illustrative of such multi-componentcompositions:

Example III Per cent Pennsylvania parailin-base oil, SAE 20 97.45Calcium naphthenoxy-stearate 2.5 Cyclohexylamine oleate 0.05

In this composition, the cycloherwlamine oleate serves as a corrosioninhibitor.

Example IV Per cent Mid-Continent paramn-base oil, SAE 40 94.9 Bariumnaphthenoxy-stearate 3.6 Refined sulfurized sperm oil 1.5

In this composition, the sulfurized sperm oil serves as a combinedextreme pressure agent and corrosion inhibitor.

Example V Per cent Mid-Continent paraifin-base oil, SAE 30 98.4

Chromic naphthenoxy-stearate 1.5 Tri-orthocresyl-phosphite 0.1Poly-dimethyl-silicone 0.001

In this composition, the tri-orthocresyl-phosphite serves as a bearingcorrosion inhibitor, and the poly-dimethyl-silicone serves as ananti-foam agent.

' Example VI Per cent Parafiin base oil, SAE 20 95.5 Zincnaphthenoxy-stearate 1.5 Aluminum naphthenoxy-stearate 1.5 Refinedsulfurized sperm oil 1.5 Poly-dimethyl-silicone .001

Example VII Per cent Califorma naphthenic oil, SAE 30 97.5 Cadmiumnaphthenoxy-stearate 1.0 Nickel naphthenate 1'.0 Chlorinated paraflin0.5

In this composition, the chlorinated parafiin serves as an extremepressure agent, and the nickel naphthenate serves as a bearing corrosioninhibitor.

Other modes of applying the principle of my invention may beemployedinstead of those explained, change being made in the ingredientsor proportions thereof, provided the compositions stated by any of thefollowing claims be obtained.

1, therefore, particularly point out and distinctly claim as myinvention:

1. A lubricating oil composition essentially comprising a majorproportion of a hydrocarbon" oil of lubricating viscosity and betweenabout 0.1 and about 5.0 per cent by weight of the composition of anoil-soluble polyvalent metal salt of naphthenoxy-stearic acid.

2. A lubricating oil composition according to claim 1, wherein saidmetal is selected from the class consisting of the metals of groups IIand VIII of the periodic. system.

3. A lubricating oil composition according to claim 1, wherein said saltis a nickel naphthenoxy-stearate.

ALBERT G. ROCCHINI.

REFERENCES crrEo The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,120,119 Steiner June 7, 19382,252,087 McNab Aug. 12, 1941 Byrket Apr. 21, 1942

